The long-term objective of this proposal is to understand how the water structure around a particular amino acid stabilizes of protein in its folded state. The specific aim of this proposal is to elucidate the relationship between amino acid sequence and protein solvent structure using the protein crambin. Water is essential for enzymatic activity of proteins, presumably through stabilizing the folded form of an enzyme. It also competes with substrates and drugs for binding sites on proteins. Thus the nature and stability of the water structure at an active site can influence activity. This proposal will investigate the nature of protein-solvent interactions. The health relatedness of this proposal is to the activity of enzymes, such as those in metabolism, to the design of new drugs to interact with enzymes and to the freezing of biological materials, where the water structure at the protein surface is important for the viability of the material. The goals of this proposal will be accomplished by genetic engineering and single crystal X-ray diffraction analysis at atomic resolution. Crambin is hydrophobic, plant seed protein (MW 4700) that is unique because crystals of it diffract beyond 0.83 angstrom, have 90% of its crystallographic data observed at this resolution limit, and contain solvent regions that are nearly completely ordered at 140 K. In this proposal, we will design and produce mutants of crambin which will change the nature and shape to the surface of the protein and crystallographically determine the structures of the mutant proteins. We synthetic gene for crambin which has already been cloned and expressed with by others. Crambin is well-suited for this investigation because, since the resolution of the crystals is so exceptional, it should be possible to directly observe small changes in the protein atomic arrangement and solvent structure induced by mutations, which will in turn lead to an understanding of the principles of protein hydration and stability.